server: Use local inbound var in version handler.

This modifies the OnVersion handler for server peers to use a local
variable for the inbound status of the peer in order to avoid grabbing
the mutex multiple times.

While here, it also does some light cleanup.  There are no functional
changes.

Backported from Decred.

server.go

@@ -405,8 +405,9 @@ func (sp *serverPeer) OnVersion(_ *peer.Peer, msg *wire.MsgVersion) *wire.MsgRej
 	// NOTE: This is done before rejecting peers that are too old to ensure
 	// it is updated regardless in the case a new minimum protocol version is
 	// enforced and the remote node has not upgraded yet.
+	isInbound := sp.Inbound()
 	addrManager := sp.server.addrManager
-	if !cfg.SimNet && !sp.Inbound() {
+	if !cfg.SimNet && !isInbound {
 		addrManager.SetServices(sp.NA(), msg.Services)
 	}
 
@@ -418,7 +419,7 @@ func (sp *serverPeer) OnVersion(_ *peer.Peer, msg *wire.MsgVersion) *wire.MsgRej
 
 	// Reject outbound peers that are not full nodes.
 	wantServices := wire.SFNodeNetwork
-	if !sp.Inbound() && !hasServices(msg.Services, wantServices) {
+	if !isInbound && !hasServices(msg.Services, wantServices) {
 		missingServices := wantServices & ^msg.Services
 		srvrLog.Debugf("Rejecting peer %s with services %v due to not "+
 			"providing desired services %v", sp.Peer, msg.Services,
@@ -428,6 +429,54 @@ func (sp *serverPeer) OnVersion(_ *peer.Peer, msg *wire.MsgVersion) *wire.MsgRej
 		return wire.NewMsgReject(msg.Command(), wire.RejectNonstandard, reason)
 	}
 
+	// Update the address manager and request known addresses from the
+	// remote peer for outbound connections.  This is skipped when running
+	// on the simulation test network since it is only intended to connect
+	// to specified peers and actively avoids advertising and connecting to
+	// discovered peers.
+	if !cfg.SimNet && !isInbound {
+		// After soft-fork activation, only make outbound
+		// connection to peers if they flag that they're segwit
+		// enabled.
+		chain := sp.server.chain
+		segwitActive, err := chain.IsDeploymentActive(chaincfg.DeploymentSegwit)
+		if err != nil {
+			peerLog.Errorf("Unable to query for segwit soft-fork state: %v",
+				err)
+			return nil
+		}
+
+		if segwitActive && !sp.IsWitnessEnabled() {
+			peerLog.Infof("Disconnecting non-segwit peer %v, isn't segwit "+
+				"enabled and we need more segwit enabled peers", sp)
+			sp.Disconnect()
+			return nil
+		}
+
+		// TODO(davec): Only do this if not doing the initial block
+		// download and the local address is routable.
+		if !cfg.DisableListen /* && isCurrent? */ {
+			// Get address that best matches.
+			lna := addrManager.GetBestLocalAddress(sp.NA())
+			if addrmgr.IsRoutable(lna) {
+				// Filter addresses the peer already knows about.
+				addresses := []*wire.NetAddress{lna}
+				sp.pushAddrMsg(addresses)
+			}
+		}
+
+		// Request known addresses if the server address manager needs
+		// more and the peer has a protocol version new enough to
+		// include a timestamp with addresses.
+		hasTimestamp := sp.ProtocolVersion() >= wire.NetAddressTimeVersion
+		if addrManager.NeedMoreAddresses() && hasTimestamp {
+			sp.QueueMessage(wire.NewMsgGetAddr(), nil)
+		}
+
+		// Mark the address as a known good address.
+		addrManager.Good(sp.NA())
+	}
+
 	// Add the remote peer time as a sample for creating an offset against
 	// the local clock to keep the network time in sync.
 	sp.server.timeSource.AddTimeSample(sp.Addr(), msg.Timestamp)
@@ -439,59 +488,6 @@ func (sp *serverPeer) OnVersion(_ *peer.Peer, msg *wire.MsgVersion) *wire.MsgRej
 	// is received.
 	sp.setDisableRelayTx(msg.DisableRelayTx)
 
-	// Update the address manager and request known addresses from the
-	// remote peer for outbound connections.  This is skipped when running
-	// on the simulation test network since it is only intended to connect
-	// to specified peers and actively avoids advertising and connecting to
-	// discovered peers.
-	if !cfg.SimNet {
-		// Outbound connections.
-		if !sp.Inbound() {
-			// After soft-fork activation, only make outbound
-			// connection to peers if they flag that they're segwit
-			// enabled.
-			chain := sp.server.chain
-			segwitActive, err := chain.IsDeploymentActive(chaincfg.DeploymentSegwit)
-			if err != nil {
-				peerLog.Errorf("Unable to query for segwit "+
-					"soft-fork state: %v", err)
-				return nil
-			}
-
-			if segwitActive && !sp.IsWitnessEnabled() {
-				peerLog.Infof("Disconnecting non-segwit "+
-					"peer %v, isn't segwit enabled and "+
-					"we need more segwit enabled peers", sp)
-				sp.Disconnect()
-				return nil
-			}
-
-			// TODO(davec): Only do this if not doing the initial block
-			// download and the local address is routable.
-			if !cfg.DisableListen /* && isCurrent? */ {
-				// Get address that best matches.
-				lna := addrManager.GetBestLocalAddress(sp.NA())
-				if addrmgr.IsRoutable(lna) {
-					// Filter addresses the peer already knows about.
-					addresses := []*wire.NetAddress{lna}
-					sp.pushAddrMsg(addresses)
-				}
-			}
-
-			// Request known addresses if the server address manager needs
-			// more and the peer has a protocol version new enough to
-			// include a timestamp with addresses.
-			hasTimestamp := sp.ProtocolVersion() >=
-				wire.NetAddressTimeVersion
-			if addrManager.NeedMoreAddresses() && hasTimestamp {
-				sp.QueueMessage(wire.NewMsgGetAddr(), nil)
-			}
-
-			// Mark the address as a known good address.
-			addrManager.Good(sp.NA())
-		}
-	}
-
 	// Add valid peer to the server.
 	sp.server.AddPeer(sp)
 	return nil